Electric furnace



ELECTRIC FUR ETT.

NACE.

APPLICATION FILED OCT. I, 1919.

Patented Jan. 31, 1922.

3 SHEETS-SHEET I.

M. H. BENNETT. ELECTRIC rumma- APPUCATIOK FILED OCT. 1. 1919- Patented Jafi. 31,1922.

. 3 SHEETSSHEET 2.

To TRANSFORMER M. H. BENNETT.

ELECTRIC FURNACE.

APPLICATION FILED 0.CT.1. 1 919;

Patented Jan. 31, 1922.

3 SHEETS-SHEET 3- TRANSFORMER To Gausnn'ron cmreo sures PATENT oar ice.

IOBBIS H. BENNETT, OF 'WATEBBURY, CONNECTICUT; ASSIGNOB TO SCOVILL MANU- FACTUBING COMPANY, OF WATEBIBUBY, CONNECTICUT, A CORPORATION OF CON- NECTICU T.

ELECTRIC FURNACE.

To all whom it may concern:

Be it known that I, MORRIS H. BENNETT, a citizen of the United States, residing at Waterbury, county of New Haven, and State 6 of Connecticut, have invented certain new and useful Improvements in Electric Furnaces, fully described and represented in the following specification and the accom-' panying drawings, same.

This invention relates to improvements in an electric furnace working on polyphase currents, the current being delivered to the charge by electrodes.

In an electric furnace working on a polyphase current which is delivered to the charge-b electrodes, there is set up 1n the area enc osed by the electrodes. a rotating magneticfield which may be termed the inner electrode field. The magnetic lines constituting this field are concentrated in the area enclosed by the electrodes, so that a strong field is produced which has a tendency to cause the metal of thecharge 1n the area enclosed by the electrodes to move in the direction of the rotation of the field, and when the metal is molten, will move it.

Due to the current flow in the electrodes, there is also set up in the area surrounding 8 the electrodes, i. e., the area between them and the furnace wall, :a. rotating magnetic field which may be termed the outer electrode field. The direction of this field is oposite to that of the inner electrode field. ii' lhe magnetic lines are not, however, concentrated in this area, but they are, on the contrary, divergent. This outer electrode field is, therefore,weak, and, so far as producing any substantial moving effect on the metal is concerned, its effect may be neg lected..

The present invention has for its ObJBClS to produce an improved electric furnace working on a polyphase current which is directly delivered to the charge in the furnace,-as by electrodes, the construction being such that there is set up a rotating magnetic field which is additional to the inner and outerrotating magnetic field operating to increase the movement of the metal, thus enabling better'mixing and increased heating'efiects to beobtained.

forming a part of the n the drawings:

igure 1 is a plan view of an improved 6 furnace embodying the'invention;

' Specification of Letters Patent. Patented Jan, 31, Application filed October 1,1919. Serial 1'0; 327,788.

which case, the rotatin Figure 2 is a section on the line 2-2 of tion embodying the invention;

Flgure 4 is an underside plan view of the 60 construction shown in Fig. 3;

Figure 5 is a perspectiveview of another modified construction of furnace embodying the invention.

Constructions embodying the invention will include in a furnace working on a polyphase heating current which isso delivered to the charge as to set up a rotating magnetic field therein, means for setting up in the charge a rotatingv magnetic field which is ad ditional to and coacts with the first named field, the effect of such additional field being directed towards increasing the movement of the molten metal and increasing the heating efi'ect.

Referring to Figs. 1 and 2, 1 indicates the metal shell, 2 the brick lining, 3 the refractory lining. Three electrodes tare provided for supplying a three-phase current to the charge in the furnace, these electrodes having terminals 5. Instead, however, of leading directly away from the electrodes, the leads 6 are connected to bus bars 7'Which are carried down the sides of the furnace and are supported inside the metal casing. The leads which connect the bus bars to the transformer are indicated at 9. Electrode positioning devices are diagramatically indicated, these comprising cables 10 connected to the electrode terminals and to drums on worm shafts 11, these shafts being operable by worms 12 on hand wheel shafts 13.

\Vith this constructiom'the polyphase currentdirectly delivered to the charge by the electrodes 4 will set up a concentrated rotat' ing magnetic field in the area lying within the electrodes, which field will tend to rotate the metal in one direction or the other according to the polarity of the current.

The currentfiowing' in the bus bars which run alongside the charge in the furnace, will also set up a rotating magnetic field which is concentrated in the area enclosed by the bus bars. The best effects will be produced where the bus bars are, as shown, parallel with the electrodesand opposite them, in

magnetic field set up by the bus bars .Wlll rotate in planes. which are parallel to the plane of the surface of the charge. This concentrated ro- Fi 1'- l Figu re 3-illustrates a modified constructating bus bar field exercises a strong rotatmg effect on the metal in the area between the electrodes and the furnace wall. If the 1 polarity of this field be such that its direction two fields will together exercise a rotating efi'ect on the'metal. If its direction be opposite to that just described, the rotating magnetic field set up by the bus bars will buck or oppose the outer electrode field, but

it will be strong enough to rotate the metal,

notwithstanding the opposing effect of this outer field. Of course, the best mixing effect will be obtained where the outer electrode field and the bus bar fieldhave the same direction, as then these fields reenforce each other and the force tending to move the 'metal is increased.

The bus bar construction just described is also effective in setting up eddy currents in the charge so that an increased heating effeet is produced, especially where metals of good conductivity, such as copper, are being melted.

In the construction so far described,the bus bars are shown as running inside the casing. This feature of the construction is important. In most furnace constructions, the exterior wall of the furnace consists of ma etic material, viz., an iron shell. If

the us bars be placed outside of the iron shell, this magnetic material acts as a magnet1c shield, and cuts down, to some extent,

' the efi'ectiveness of the field developed by the current in the bus bars. Of course, if the exterior of the furnace is not constructed of magnetic material, the bus bars may be located on the outside of the furnace. In some cases, furthermore, while the shell of the furnace may consist of magnetic material, it may be so thin, or otherwise of such construction, that the shell will not so seriousl impair the field as to make it substantial y ineffective. In such cases, the bars may be located on the exterior of the furnace if the loss of efiiciency of the field is not regarded as material.

In many cases, it may be desirable to increase the effect of the additional magnetic field as compared with the effect of the fieid' which would be established b a. 'simple bus bar or conductor. To accomp ish this, a dis-z" tributed current carrier may be provided, this carrier, as shown in Figs. 3 and 4, comprising a-pllurality of bus bars 7 for each electrode, t ese bus bars being arranged 1n parallel. This carrier may also be led un derneath the charge, as shown in Figs. 3 and. 4. When this is done, the conductors formingthis carrier may be tapered as they approach the center of the charge, so that each set of bus bars is fanned out underneath the charge. By employing a distributed current the furnace, tend'to cause a mixing movement of the metal. The coacting field setup by locating the carrier underneath the charge tends to cause a mixing movement of the metal in a direction which is different from the movement induced by the other field or fields. This still furtherincreases the mixin efi'ect and also the heating effect.

11 the construction so far described, the additional coacting fields have been produced by so arranging the flow of the heating current into the electrodes that it will establish a field or fields additional to the .Qelds established by the electrodes, and substantially all the current is utilized in thus producing the field or fields. It is, of course, obvious that only a art of the current may be thus utilized. or instance, a shunt may be employed to send the desired part of the current through the bus bars. Further, the current flow, which produces these magnetic fields need not be the flow into the electrodes.

In the construction illustrated in Fig. 5, the terminals 5 of the electrodes are shown as connected with leads 15 which rundirectly to a transformer, indicated at 16. Conductor coils 17 are, as shown in this construction, located between the shell and the brick work, these conductor coils being directly connected by wires 20, 21, 22 running to a generator. In this construction, as will be readily understood, a coacting field is produced'by a that changes and variations may be made in these constructions and the invention embodied'in other constructions so long as the spirit and scope thereof as herein set forth is not departed from.

What is claimed is:

. 1. In an electric furnace, the combination with means for so delivering polyphase heating current directly to the charge as to set up a rotating magnetic field or fields in. the charge, means for setting up current flow in proximity to the charge which establishes a rotating magnetic field in the charge additional to and coacting with the field or fields established by the polyphase i heating current. p

2. In an electric furnace, the combination with means for so delivering a polyphase heating current directly to the charge as to set up therein a rotating magnetic field or fields, of conductors for carrying polyphase current arranged in such proximlty to the charge as to set up therein a rotating magnetic field which is additional to and coacts with the field or fields established by the current delivery directly to'the charge.

3. In an electric furnace, the combination with electrodes for so delivering polyphase heating current directly to the charge as to set up a rotating magnetic field or fields in the charge, of conductors for carrying polyphase currents located in such proximity to the charge as to set up therein a rotating magnetic field which is additional to and coacts with the rotating magnetic electrode field or fields.

4. In an electric furnace, the combination with means for so delivering a polyphase heating current to the charge as to set up a rotating magnetic field or fields in the charge, of conductors for carrying polyphase currents arranged at the side of the charge and underneath the charge and in such proximity thereto that these currents set u rotating magnetic fields in the charge,

the eld due to the flow of the current at the side of the charge meet with the field or fields established by e heating current delivered to the char 5. In an electric furnace, t e combination with electrodes for so delivering polyphase heatin current as to set up a rotating magnetic eld in the charge, of conductors for carrying olyphase currents arranged in such proxlmity to the charge as to set up a rotating magnetic field or fields therein.

6. The combination, in an electric furnace, with means for delivering aheating current to the charge, of means for setting up a rotating magnetic field or fields underneath the charge, whereby mixing and stirring of the charge at the bottom is secured.

' 7 In an electric furnace, the combination with means for so delivering a polyphase heating current to the charge as to set up a rotatin magnetic field or fields in the charge, 0 a distributed current carrier for polyphase currents arranged in such proximity to the charge that a rotatinghmagnetic field is set up in the charge whi is additional to and coacts with the field or fields established by the heating current.

8. In an electric furnace, the combination with electrodes for so delivering a polyphase heating current to the charge as to set up a rotating magnetic field or fields in the charge, of a distributed current carrier for polyphase currents located at the side of and underneath the charge and in such proximity thereto that the flow .of current in that part of the carrier which is alongside the charge sets up a rotating magnetlc field or fields in the charge which coacts with the electrode field and other rotating -magnetic fields are set up in the charge by alongside the charge, said current settingup a magnetic field or fields which is additional to and coacts with the electrode field.

10. In an'electric furnace having three electrodes arranged to deliver a three-phase current to the charge, whereby a rotating magnetic field is set up therein, of conductors carrying a three-phase current located in such proximity to the charge that the current in the conductors sets up rotatin magnetic field or fields in the charge whic iis illdltlonfll to and coacts with the electrode 11. In an electric furnace having three electrodes arranged to deliver a threehase current to the charge in the furnace w ereby a. rotating magnetic field is set up therewith the electrode field, and the fields set up by the flow of current in that part ofthe conductors underneath the charge act on the metal in the bottom of the char In testimony whereof, I have ereunto set my hand.

MORRIS H. BENNETT. 

